Media devices, such as a set top box, stereo, television, computer system, game system, or the like, are often configured to receive operating instructions from a user via a remote control. The remote control communicates user instructions to the media device using an infrared signal, radio signal, or other suitable wireless signal.
The remote control typically is powered from a battery or other portable power source. Over time and use, the battery discharges to a point where it is no longer able to provide sufficient power for correct operation of the remote control. When such low power situations arise, a microcontroller that controls operation of the remote control is typically placed in a reset mode. Prior to entering the reset mode, information critical to operation of the microcontroller is actively stored in a non-volatile memory device. At some point, the battery is replaced and/or recharged, such as when the user removes the discharged batteries and replaces them with new, fully charged batteries.
An abrupt complete loss of power is very undesirable, as information stored in a non-volatile memory device used by the microcontroller may be lost. For example, the user might remove the batteries prior to the microcontroller saving critical operating information. When the user removes the batteries, all power to the microcontroller is abruptly removed, any data save processes running will be in an unknown state.
One or more voltage detection circuits may be used to monitor voltage provided by the battery and/or the capacitor so that the microcontroller can take appropriate protective actions to preserve critical functions and/or information when power levels are determined to be close to the point at which data saves are unreliable, or operation becomes unreliable. The saving of critical information and/or entry into reset mode by the microcontroller is based on the detected operating voltage dropping to a predefined voltage usually referred to as the “critical voltage”.
Due to variations from one remote control to the next remote control, the predefined critical voltage is determined by design and/or by testing of sample devices. To account for device manufacturing tolerances, voltage margins are added so that the microcontroller has a reliable amount of power for entry into reset mode. Thus, the designed critical voltages are predefined at higher values than the actual minimum voltage at which the microcontroller must save critical data or enter reset to avoid damage, loss of vital information, and/or incorrect operation.
The above-described variations between remote controls may be caused, for example, by semiconductor process variation, variations in device loadings, and/or time delays of interval voltage detection circuits. As a consequence, the optimum critical voltage may vary from one remote control to another.
Similar problems may be encountered in other types of microcontroller-based electronic devices that operate on battery power. Accordingly, there is a need in the arts to more accurately determine the optimal critical voltage at which the microcontroller must save data and/or begin entry into a safe or reset mode to avoid damage and/or loss of vital information.